“Jackass,” as an MTV series and even more so as a less-censored big-screen franchise, felt new and different and outrageous, even if you could trace its component parts to ancestors as far afield as “Candid Camera,” circus sideshows and Antonin Artaud’s Theater of Cruelty.

Watching a jockstrap-clad Johnny Knoxville dangle over an alligator pit with chicken parts between his legs, or Steve-O intentionally give himself paper cuts, or the late Ryan Dunn inserting a toy car into his own nether regions gave the show’s fans a distinct kind of pleasure, causing them to erupt in sounds that were somewhere between laughing and shrieking in horror.

There’s not so much of that shock of the new in the latest “Jackass” entry, “Bad Grandpa,” but even if the film feels like the show’s old stunts thrown into a blender with “Borat,” “Little Miss Sunshine” and some sketches from MTV’s post-“Jackass” shock-comedy “Wonder Showzen,” the laughs are still there, even if the shrieks have died down.

Knoxville, who’s earned the right to mellow out a little after breaking most if not all of his bones for his art, stars (in heavy effects makeup) as senior citizen Irving Zisman, who’s ready to party after the death of his wife Ellie (Catherine Keener). Since Irving’s daughter is going to jail on a drug charge, however, Irving gets stuck driving cross-country to deliver his young grandson Billy (Jackson Nicoll, “Fun Size”) to the kid’s ne’er-do-well dad.

At first, it seems like the movie is giving us these characters just as a framework for Knoxville and Nicoll to do outrageous things in front of unknowing passersby. That happens — Irving shakes his saggy body for the horrified female patrons at a male-stripper bar, Billy asks random people to be his new dad — but the bare-bones structure isn’t just here as a foundation for the jokes.

“Bad Grandpa” actually expects us to be interested in the plot, to the extent that Knoxville and Nicoll interact as Irving and Billy even they’re the only ones on camera. (They’re like the hero of “Holy Motors,” who stays in character even when he’s not sure if he’s being filmed.) The earlier “Jackass” movies worked just fine as assemblages of sketches; this time out, we’re supposed to invest in this meager story, and it’s a bit distracting.

Still, when the three-act structure gets shoved to the side for fun and games, “Bad Grandpa” delivers some of the heartiest laughs I’ve had all year. People who always found “Jackass” to be distasteful and cruel won’t change their minds, but fans will find themselves gasping over what Knoxville and the very game Nicoll can do with an air bag, a bingo parlor, a funeral, a wedding, a grocery store and a child beauty pageant.

If the “Jackass” movies are to continue with Knoxville and his cohorts playing characters and pulling hidden-camera stunts on the unsuspecting, then great. But if five credited writers can’t figure out a way for them to blow up their cake and eat it too, then maybe 90 minutes of unrelated sketches isn’t such a bad thing.

Alonso Duralde, TheWrap's reviews editor, has written about film for Movieline, Salon, MSNBC.com. He also co-hosts the Linoleum Knife podcast and regularly appears on Who Shot Ya? and Breakfast All Day. Senior Programmer for the Outfest Film Festival in Los Angeles, he is also a consultant for the USA Film Festival/Dallas, where he spent five years as artistic director. A former arts and entertainment editor at the Advocate, he was a regular contributor to FilmStruck and to "The Rotten Tomatoes Show" on Current. He is the author of two books, "Have Yourself a Movie Little Christmas" (Limelight Editions) and "101 Must-See Movies for Gay Men" (Advocate Books).